Many methods and materials have been explored to achieve biocompatibility of implantable medical devices (IMD). Implantable medical devices, as used herein, include any blood-contacting medical device that is implanted in the body, chronically or otherwise, including, but not limited to, blood-contacting surgical tools, implantable cardiac devices, implantable monitors, biological sensors, implantable drug delivery devices, catheters, artificial blood vessels and stents. For IMDs, it is especially desirable that there be minimal friction during implant to facilitate implant dynamics. To this end, IMDs have been coated with materials which increase wet lubricity, thereby reducing procedure time, insertion forces and patient discomfort. Lubricity also reduces tissue irritation and damage and provides greater control and maneuverability of the device during implant. Wet lubricity for hydrophobic surfaces may be achieved using hydrophilic coatings. Such coatings also improve biocompatibility by, for example, reducing protein adsorption and platelet adhesion and other blood interactions, as well as resisting bacterial adhesion.
For example, lead insulation materials have been surface-coated with a UV-cured polyvinylpyrrolidone (PVP) from SurModics, Inc. of East Prairie, Minn., using PHOTOLINK® chemistry coating technique to achieve the benefits of wet lubricity and hydrophilic coatings. This coating technique involves photochemical covalent bonding of the coating molecules to the insulation material substrate and requires several steps, including lead cleaning, PVP solution preparation, plasma treatment, lead coating, photo activation and cleaning. This process is complex and difficult to control and can lead to poor quality coatings.
Lubricious surfaces can also be prepared by chemical grafting techniques using other hydrophilic materials, such as polyethylene oxide (PEO), referred to also as polyethylene glycol (PEG), which can be grafted to the polymer substrate either as end segments or branches to the back bone of the polymer. The existing techniques and materials, however, do not provide effective lubricious surfaces on medical devices formed of materials including silicone rubber or silicone polyurethane copolymer (SPC). Silicone rubber and SPC are common insulation materials used on medical leads.
What are needed, therefore, are new materials to achieve highly lubricious coatings for implantable medical devices, which are particularly useful for preparing lubricious coatings on silicone and SPC leads or other silicone rubber or SPC medical devices. The present invention provides PEO and silicone copolymers to satisfy these and other needs, and provides further related advantages, as will be made apparent by the description of the embodiments that follow.